Example of right censored mRNA expression data with multiple censoring levels.

Case A: The threshold cycle of the gene of interest E2 for case A is 31.1. The threshold cycle of the housekeeping gene (HKG) H12 is 12.6. The Δct value is 18.5 (31.1–12.6 = 18.5). In this case no censoring is present.
Case B: The threshold cycle of the gene of interest G12 for case B exceeds 39, is not quantifiable any more, and consequently, is right censored. The threshold cycle of HKG H2 is 12.4. The Δct value is 26.6 (39–12.4 = 26.6). The Δct value contains the right censored value of 39, thus the resulting Δct value is also right censored. Consequently, the Δct value has to be interpreted as greater than 26.6.
Case C: The threshold cycle of the gene of interest D2 for case C exceeds 39, is not quantifiable and also right censored. The threshold cycle of HKG D1 is 13.1. The Δct value is 25.9 (39–13.1 = 25.9). The Δct value contains the right censored value of 39, thus the resulting Δct value is also right censored. The Δct value has to be interpreted as greater than 25.9. However, as the threshold cycle of the HKG is different to case B (26.9 vs. 25.9) the resulting right censored Δct value has a different censoring level than in case B.
Thus, Δct values may be right censored data at different censoring levels.